The Large Far-ultraviolet Flux Deficiency of α Doradus (B8 IIIp Si)

The far-UV spectral energy distribution of α Dor recorded by IUE is compared to that of the constant and normal star ζ Dra, which has similar fundamental parameters. α Dor has much less flux than ζ Dra shortwards of 1800 A, due to the accumulation of very strong absorption lines of Si ii, in particular autoionization lines around 1400 A. Two spectra of α Dor separated by 9 hr (i.e., much less than the rotational period) show evidence of modest variability shortwards of 1800 A.